Complete Technical Specifications for BV Grade D Marine Structural Steel Plates

I. Detailed Chemical Composition

The chemical composition of BV Grade D is designed based on the principles of low alloy content and high purity. By strictly limiting harmful elements and adding grain-refining elements, the material’s strength, toughness, and weldability are ensured. The specific composition requirements are as follows:

Key Points:

Grain Refinement Treatment Requirements:

The BV specifications clearly stipulate that Grade D steel plates with a thickness greater than 25 mm must undergo kettle treatment and grain refinement (Al or Al+V grain refinement). This is the key process requirement that distinguishes Grade D steel from Grade A/B steel.

Carbon Equivalent Control:

The carbon equivalent formula is CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15. This is the core indicator for assessing a material’s weldability.

A lower CE value indicates lower susceptibility to cold cracking during welding, making it suitable for large-scale welding operations in shipyards.

II. Mechanical Property Specifications

The mechanical properties of BV Grade D shipbuilding steel plates strictly meet the load-bearing requirements of ship hull structures under various operating conditions. Key specifications are as follows:

Explanation of Low-Temperature Toughness:

The impact test temperature for BV Grade D steel plates is -20°C, which is the core feature distinguishing it from Grade A (20°C) and Grade B (0°C).

This specification ensures that the ship’s hull structure can resist low-temperature brittle fracture during winter navigation or operations in high-latitude waters.

III. Dimensional Range and Supply Specifications

The supply dimensions of BV Grade D steel plates cover the processing requirements of major shipyards:

Special Specifications: For thicker grades (e.g., >50 mm), BV specifications impose stricter requirements on delivery conditions and impact properties; delivery in TMCP or normalized condition is typically required to ensure core properties.

IV. Delivery Condition Classification

Depending on thickness and performance requirements, BV Grade D is available in various delivery conditions, which must be specified at the time of purchase:

The Mill Test Certificate (MTC) clearly specifies the delivery condition and rolling process, which serves as an important basis for tracing the quality of steel plates.

V. Summary

1) The core technical specifications of BV Grade D Shipbuilding Steel Plate can be summarized as follows:

2) Chemical Composition: Low carbon + low P/S + Al for grain refinement; CE ≤ 0.40% to ensure weldability;

3) Mechanical Properties: Yield strength ≥ 235 MPa, tensile strength 400-520 MPa, impact strength at -20°C ≥ 27 J, meeting the structural requirements for ship hulls in conventional maritime environments;

4) Dimensions: Thickness 4-260 mm, covering a wide range of products including ship plates and profiles;

5) Delivery Conditions: AR, CR, NR, TMCP, Q+T, etc., selected based on thickness and design requirements.

During procurement and design selection, special attention should be paid to the delivery condition requirements corresponding to the thickness, as well as the BV factory approval status, to ensure that the material meets BV specifications from chemical composition to mechanical properties.

For polar-class vessels operating at temperatures below -20°C, it is recommended to select materials meeting the BV Grade E (-40°C impact) standard.